The present invention relates generally to a super high rise tower for use as an observation platform and/or support for a super high rise antenna. In particular, the invention relates to a super high rise tower having a height of at least 400 meters above the ground and consisting mainly of a prestressed cable net adapted to resist wind and earthquake loads.
A number of world famous super high rise towers have been constructed in the past, including, for example the Tokyo Tower, the Eiffel Tower and the Moscow Tower. These towers are all of generally conventional construction using stacked steel frames and a truss configuration. Typically a prefabrication system is employed as the construction method for these towers, with the steel frames and other construction elements being sequentially lifted and hung by cranes, helicopters or the like for assembly.
Since a conventional high rise tower is constructed by stacking steel frames as a truss construction, when the structure is subjected to a horizontal load such as a wind load, the structure bends in the same direction as the load. A schematic illustration of this effect is shown in FIG. 1, which magnifies a model of a horizontal load Q and the amount of bending of a structure A when the wind load Q is applied to structure A. As seen therein, the structure A bends with the wind and thus deflects substantially at its top. In addition, the opposite sides of the structure are subjected to opposed stresses of tension and compression. As a result of this movement, conventional high rise towers are apt to shake or vibrate when subject to wind or earthquake loads. Such shaking affects the force-proof and earthquake-proof characteristics of the tower, e.g., extremity distortions and buckling will occur at the tension and compression sides of the tower, respectively. In addition, the swaying which will occur in the tower even under normal conditions will make use of the tower uncomfortable for people in the upper portions thereof. Thus, the vibration and swaying problems inherent in conventionally constructed towers prevent truly super high rise towers from being constructed.
Moreover, the conventional tower construction method which hangs steel frames and the other construction elements with cranes and helicopters is suitable for constructing only up to certain heights. At extreme heights working conditions are dangerous and it is very expensive using conventional techniques.
Accordingly, it is an object of the present invention to construct super high rise towers of 400 meters and more in height which will have improved wind and earthquake load resistance and reduced sway.
Another object of the present invention is to build super high rise towers efficiently and economically.
Yet another object of the invention is to build a super high rise tower using a prestressed cable network to reduce movements of the tower under load.
In accordance with an aspect of the present invention, a super high rise tower is provided which consists of a central core for supporting the weight of the tower and receiving the compression forces therein and a prestressed cable net around the core. Prestressing of the cable net reduces movements of the tower under wind and earthquake loads so that vibration and sway in the tower are substantially reduced as compared to conventionally constructed towers. Thus, the tower has improved wind force-resistance and earthquake-resistance characteristics are remarkably improved. As a result, it is possible to build a tower higher than with conventional techniques.
Of course, since the volume of steel used in towers of the present invention is significantly less than that of steel frame construction, it is much easier to process and assemble the tower and construction costs are remarkably reduced.
The above and other objects, features and advantages of the invention will be apparent to those skilled in the art from the following detailed description of illustrative embodiments thereof when read in connection with the accompanying drawings wherein: